Overrunning bi-directional clutches are known, see for example U.S. Pat. Nos. 6,409,001; 7,004,875; and 7,037,200. Such clutches are mounted between two coaxial shafts and are used to transfer power between the two shafts. The clutch is fixed to a first shaft and selectively engages the second shaft so as to transfer power between the two shafts. Typically, the first shaft is the power input shaft and typically, the first shaft is also the inner shaft of the two shafts. The output shaft or second shaft can be a geared wheel.
Overrunning bi-directional clutches comprise a fixed ring, a slipper ring, cylindrical rollers which are housed between the two rings and may have an actuator. The fixed ring and the slipper ring are coaxial cylindrical rings with opposing faces. Each of the opposing faces has concave bearing surfaces which define pockets. Each pocket houses a roller.
The slipper ring has an axial groove or slit that extends both radially and axially through the ring. The slit allows the slipper ring to move radially under force and the memory inherent in the material from which the slipper ring is made allows the ring to return to a rest position once the force is withdrawn. The fixed ring is mounted onto the first shaft while the slipper ring is spaced in close proximity to the second shafts such that when the slipper ring moves radially, it engages the second shaft, thereby transferring power between the two shafts. Once the force is removed from the slipper ring, it returns to its rest position and no longer engages the second shaft.
The actuator is used to maintain the clutch in the freewheel mode and to move the clutch to the lock mode. Typically, the actuator is a radial mounted moveable pin which is fixed to the fixed ring and retractable from the slipper ring. When the actuator engages both rings the two rings are coupled and the clutch is in the freewheel mode. In the freewheel mode, the opposing concave bearing surfaces are aligned with each other and the rollers rest in the bottom of each of the opposing concave surfaces. When the actuator pin is withdrawn from the slipper ring, the two rings move relative to one another and the rollers move out of the bottom of the opposing concave surfaces and rise up along diagonally opposing surfaces of the pocket so as to force the slipper ring to move radially and to engage the second shaft, thereby transferring power between the two shafts, locking the clutch and placing the clutch in the lock mode.
One of the problems with overrunning bi-directional clutches is that once the actuator is moved to transfer the clutch from the freewheel mode to the lock mode, the clutch reacts very quickly and the overall time period is on the order of 10 to 25 milliseconds. For shafts traveling at high speeds, this shift can have a detrimental effect on the machine because the second shaft is essentially at rest and must be brought up to the speed of the first shaft instantaneously.